Life expansion
Life expansion occured in the (or Palaeozoic), a term from the Greek words palaios (παλαιός), "old" and zoe (ζωή), "life", meaning "ancient life". This geologic era is the earliest and longest of the Phanerozoic Eon. Paleozoic was a time of dramatic geological and climatic changes, and . The Cambrian period witnessed the most rapid and widespread diversification of life in Earth's history—known as the Cambrian explosion, in which most modern phyla first appeared. Fish, arthropods, amphibians, anapsids, synapsids, euryapsids and diapsids all appeared during the Paleozoic. Great forests of primitive plants covered the continents, many of which formed the coal beds of Europe and eastern North America. Towards the end of the era, large, sophisticated diapsids and synapsids were dominant, and the first modern plants (conifers) appeared. The Paleozoic Era ended with the largest extinction event in the history of Earth, the Permian–Triassic extinction event. The effects of this catastrophe was so devastating that the environment was not conducive for terrestrial life until 30 million years into the Mesozoic Era, with sea-life flourishing in at least half that time. http://www.economist.com/node/16524904 The Economist Geological formation :(See also: Day 3) ;Supercontinents merge (358.9–298.9 million years ago) The ( ), or Gondwanaland, formed from the unification of several cratons in the Late Neoproterozoic. Over time, it merged with Laurussia, in the Carboniferous, to form Pangaea . Gondwana was the largest continental landmass on Earth, covering an area of 100,000,000 km2 (39,000,000 sq mi) or 64% of today's continents. It was originally located in the Southern Hemisphere, incorporating several modern landmasses, that included Antarctica, South America, Africa, Madagascar, and Australia, as well as the Arabian Peninsula and the Indian subcontinent, which have now moved entirely into the Northern Hemisphere. Gondwana began to fragment in the Mesozoic. ;Seed-bearing plant event (319 million years ago) A whole genome duplication event in the ancestor of seed-bearing plants occurred about 319 mya.Jiao Y, Wickett NJ, Ayyampalayam S, Chanderbali AS, Landherr L, Ralph PE, Tomsho LP, Hu Y, Liang H, Soltis PS, Soltis DE, Clifton SW, Schlarbaum SE, Schuster SC, Ma H, Leebens-Mack J, Depamphilis CW (2011) Ancestral polyploidy in seed plants and angiosperms. Nature This gave rise to a series of original terrestrial biodiverse seed-producing plants that replaced the lycopsid rainforests of the tropical region. Campbell and Reece; Biology, Eighth edition By far the largest group of living gymnosperms are the conifers (pines, cypresses, and relatives), followed by cycads, gnetophytes (Gnetum, Ephedra and Welwitschia), and Ginkgo biloba (a single living species). Roots in some genera have fungal association with roots in the form of mycorrhiza (Pinus), while in some others (Cycas) small specialised roots called coralloid roots are associated with nitrogen-fixing cyanobacteria. Climatic events :(See also: Day 4) ;272.95 – 252 million years ago An unknown global warming phenomena caused an , suspect to have occurred since the Guadalupian age (272.95 Ma), that triggered a . The created a that caused the most severe conditions in Earth's oceanic history, which ultimatly led to the "The Great Dying" (Permian–Triassic extinction event) in 252 Ma. The domino effect can be explained by the . It proposes that increases in sea temperatures (and/or drops in sea levels) can trigger a catastrophic positive feedback effect on climate: first, warming causes a sudden release of from compounds buried in seabeds and seabed permafrost; second, because methane itself is a powerful , temperatures rise further, and the cycle repeats. This runaway process, once started, could be as irreversible as the firing of a gun. Biodiversity :(See also: Day 5) After the Permian–Triassic extinction event, the Mesozoic Era beings. This period spans from about 252 to 66 million years ago. Paleontologists call this period the Age of Reptiles in view of the Earth being dominated by diapsids such as Iguanodon, Megalosaurus, Plesiosaurus and Pterodactylus. The paleobotanist calls it the Age of Conifers. ;Great sea and land creatures (250–231.4 million years ago) See also: Fish About 10 million years after the Permian–Triassic extinction event, the "Great Dying" (252 mya), an explosion of a variety of fish, in the class of Teleost, appeared in the Early Triassic period. Additionally, after the quick and dynamic rebound of marine ecosystems, a diverse group of reptiles of the clade Dinosauria, appeared between 243 and 231 million years ago, The exact origin and timing of Dinosauria appearance is the subject of active research in academia. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago; their dominance continued through the Jurassic and Cretaceous periods. In the mid-Jurassic period, around 170 million years ago, the appearance of bird-like dinosaurs (which lie outside class Aves proper), existed the Archaeopteryx. These were not capable of fully powered flight, many had toothy jaws and long bony tails, thus are classed in the broader group Avialae. ;Flying creatures (120 million years ago) True birds first appeared during the Cretaceous period, around 120 million years ago. DNA-based evidence finds that birds diversified dramatically around the time of the Cretaceous–Palaeogene extinction event 66 million years ago, which killed off the pterosaurs and all the non-avian dinosaur lineages. Birds, especially those in the southern continents, survived this event and then migrated to other parts of the world while diversifying during periods of global cooling. ; End of Cretaceous period (66 million years ago) :* References Category:Theoretical History Category:1.6 Ga–66 mya